Dr. John D.M. Belgrave, Belgrave Oil and Gas Corp.
Dr. P. Chandrasekeran, Oil India Limited
S.C. Mishra, Oil India Limited
N.R. Hazarika, Oil India Limited
T. Dutta, Oil India Limited
International Oil and Gas Conference & Exhibition, Delhi, India
February 6-7, 2020.

Dr. John Belgrave

This presentation reports on the design, implementation, and performance of the first successful Cyclic Steam Stimulation (CSS) Enhanced Oil Recovery test in India. The test was conducted in the Jodhpur Sandstone reservoir of the Baghewala heavy oil field, located in North-West Rajasthan.

The Jodhpur sandstone occurs at an average depth of 1,100 m, and contains an estimated oil-in-place of 12.5 million tonnes (77 million barrels) of 14 - 17 oAPI oil. Reservoir pressure and temperature are 116 kgf/cm2 and 50 oC, respectively. Oil viscosity at reservoir conditions varies from 2,620 - 26,600 mPa.s, the variation being a result of biodegradation in the vicinity of an oil-water contact. Oil productivity on primary production ranges from 2-10 m3/day/well, with viscosity-related rod-fall problems reducing sucker-rod pump lift efficiency.

Laboratory tests indicated a 1,100-fold reduction in oil viscosity corresponding to an increase in temperature from reservoir conditions to steasm temperature at reservoir pressure. This, together with ample reservoir energy, motivated the testing of CSS in the Jodhpur.

The relatively high reservoir pressure presents exploitation challenges by steam injection. Minimum steam injection temperature will be in excess of 300 oC which exerts considerable influence on well construction and operability. And, a lost circulation zone at intermediate depth in nearly all instances has prevented the circulation of cement from reservoir depth to surface. For these reasons an earlier attempt (2006) to test CSS in a shallower formation at Baghewala resulted in almost immediate catastrophic well failure.

A comprehensive approach to well design and CSS implementation was adopted to mitigate the above stated risks. Vacuum-insulation tubing, pressurization of the casing-tubing annulus with nitrogen (avoiding the need for a thermal packer), and control of wellhead steam injection pressures have proved successful. To date, two cycles of CSS have been performed at the BGW-8 well. Steam injectivity and well productivity have exceeded expectations and casing expansion has been within design limits. On turnaround, the well has flowed for a period of three weeks and at an initial oil rate of 30 m3/day. Producing potential on pump has yet to be evaluated.

These results confirm suitability of well design and operation, and the potential for CSS to increase oil production and recovery from the Jodhpur sandstone. The information obtained sets the stage for thermal exploitation of the uphole heavy oil-bearing formations that contain an additional 60 million tonnes (370 million barrels) of heavy-oil resource.

Previous PageNext Page